Antifungal susceptibility testing of yeast isolated from corneal infections

Abstract

Antifungal susceptibility testing of yeast isolated from corneal infections INTRODUTIONFungi are opportunistic agents which rarely infect healthy corneas of immunocompetent individuals. Systemic and local underlying diseases may render the corneal tissues susceptible to infections with these organisms (1) . Trauma, specially related to organic materials, topical use of steroids and antibiotics (2)(3) , contact lens wear, surgical procedures, contamination of eye solutions, inappropriate maintenance of contact lenses (4) , systemic infections as well as any disease associated with immunodeficiency are considered risk factors for fungal eye infections (5) . In Brazil, the incidence of fungal eye infections ranges from 3.8 to 10%, depending on the site of the infection, the diagnostic tools available for fungal infections in the medical center and the seasons related to the studied period (6)(7)(8)(9) . The occurrence of keratomycosis is of great importance, not only because of diagnostic problems but also due to the severity of clinical manifestations and poor outcome despite antifungal treatment. The severity and progression of the fungal infection usually depend on the existence of Purpose: To report the antifungal susceptibility profile of yeast isolates obtained from cases of keratitis. Methods: Susceptibility testing of 15 yeast strains isolated from corneal infections to amphotericin B, fluconazole, itraconazole and ketoconazole was performed using the NCCLS broth microdilution assay. Results: Most episodes of eye infections were caused by Candida albicans. The antifungal drugs tested showed the following minimal inhibitory concentration values against yeast isolates: 0.125-0.5 µg/ml for amphotericin B; 0.125->64.0 µg/ml for fluconazole; 0.015-1.0 µg/ml for itraconazole and 0.015-0.125 µg/ml for ketoconazole. Despite the fact that all Candida isolates were judged to be susceptible to azoles, one isolate showed a minimal inhibitory concentration value significantly higher than a 90% minimal inhibitory concentration of all tested isolates. Rhodotorula rubra was resistant to fluconazole and itraconazole. Conclusions: Despite the fact that most yeast isolates from corneal infections are usually susceptible to amphotericin B and azoles, they exhibit a wide range of minimal inhibitory concentration values for antifungal drugs. The identification of strains at species level and their susceptibility pattern to antifungal drugs should be considered before determining the concentration to be used in topical antifungal formulations in order to optimize therapeutic response in eye infections.ABSTRACT

Development of a Poly-ε-Lysine Contact Lens as a Drug Delivery Device for the Treatment of Fungal Keratitis

“…19,21 The MIC found in this report (see Supplementary Material S1) is between 0.094 and 0.188 lg/mL for C. albicans cultured in both PD and PD with 10% horse serum and correlates with MIC data for ocular isolates from the literature of 0.06 to 1 lg/mL. 26,27 A concentration of AmpB, well above the MIC, is necessary to ensure adequate dosing to the cornea considering that 7% reaches the target tissues. Using serial dilutions of the stock AmpB solution, we demonstrated that AmpB incorporated into the peK hydrogels significantly reduced the growth of C. albicans compared with no AmpB, independent of the solution concentration over 18 hours.…”

“…The dose at 96 hours is still relevant compared with minimum inhibitory concentration data from the literature. 26,27 AmpB Viability After Attachment to the Hydrogels AmpB associated with the hydrogel remained stable and produced a killing effect against C. albicans for at least 48 hours (Fig. 8).…”

Antifúngicos em infecções oculares: drogas e vias de administração

“…exhibited a lower susceptibility of these organisms to KCZ compared to NTM and VCZ (50) . Other laboratory studies also showed similar results with strains of Aspergillus, Fusarium and Candida spp., which were susceptible to KCZ only at high doses (34,77) . Currently, systemic KCZ is indicated only for the adjuvant treatment of deep fungal keratitis.…”

“…), AMB is still the drug of choice. Although therapeutic success depends on using the drug for a long period (at least 4 weeks), there are few reports of drug resistance by these organisms (34) . Among filamentous fungi, especially Fusarium spp., there are reports of drug resistance (3,10) .…”

“…In several studies that evaluated the susceptibility of causative agents of fungal keratitis and endophthalmitis, only Candida species were susceptible to FCZ, and filamentous fungi (Aspergillus and Fusarium spp.) exhibited marked resistance (34,48,77,92) .…”